Documentation/Platforms/RISCV

Description

RISC-V is an open source instruction set. It is a modular with only a small set of mandatory instructions. Every other module might be implemented by vendors allowing RISC-V to be suitable for small embended systems up to large supercomputers.

Build Directions

For RV64GC:

 ./configure --target-list=riscv64-softmmu && make

For RV32GC:

 ./configure --target-list=riscv32-softmmu && make

Booting Linux

Booting 64-bit Fedora

Download the Fedora disk images Decompress the disk image:

  xzdec -d stage4-disk.img.xz > stage4-disk.img

Boot linux using RV64GC qemu:

  qemu-system-riscv64 \
   -nographic \
   -machine virt \
   -smp 4 \
   -m 2G \
   -kernel bbl \
   -object rng-random,filename=/dev/urandom,id=rng0 \
   -device virtio-rng-device,rng=rng0 \
   -append "console=ttyS0 ro root=/dev/vda" \
   -device virtio-blk-device,drive=hd0 \
   -drive file=stage4-disk.img,format=raw,id=hd0 \
   -device virtio-net-device,netdev=usernet \
   -netdev user,id=usernet,hostfwd=tcp::10000-:22

• Login: root
• Password: riscv

Booting 32-bit OpenEmbedded Images

Follow the usual OpenEmbedded build flow using meta-riscv to build for the qemuriscv32 machine. More details on doing this can be found here: https://github.com/riscv/meta-riscv/#build-image

Once the images are build you can boot them using:

 qemu-system-riscv32 \
   -device loader,file=./tmp-glibc/deploy/images/qemuriscv32/Image,addr=0x80400000 \
   -device virtio-net-device,netdev=net0 -netdev user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::2323-:23 \
   -drive id=disk0,file=./tmp-glibc/deploy/images/qemuriscv64/core-image-minimal-qemuriscv32.ext4,if=none,format=raw \
   -device virtio-blk-device,drive=disk0 \
   -object rng-random,filename=/dev/urandom,id=rng0 \
   -device virtio-rng-device,rng=rng0 \
   -kernel ./tmp-glibc/deploy/images/qemuriscv32/Image \
   -append 'root=/dev/vda rw highres=off  console=ttyS0 mem=512M ip=dhcp earlycon=sbi ' \
   -show-cursor  -nographic -machine virt -m 512 -serial mon:stdio -serial null 

The above command will open up SSH and telnet ports which can be used to communicate with the guest. It will also pass in host entropy to the guest, allowing entropy to be available on boot.

NOTE: When using OpenEmbedded it is recommended to use the runqemu script to boot QEMU. It will dynamically handle display options as well as advanced networking

Booting 64-bit OpenEmbedded Images

Follow the usual OpenEmbedded build flow using meta-riscv to build for the qemuriscv64 machine. More details on doing this can be found here: https://github.com/riscv/meta-riscv/#build-image

Once the images are build you can boot them using:

 qemu-system-riscv64 \
   -device loader,file=./tmp-glibc/deploy/images/qemuriscv64/Image,addr=0x80200000 \
   -device virtio-net-device,netdev=net0 -netdev user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::2323-:23 \
   -drive id=disk0,file=./tmp-glibc/deploy/images/qemuriscv64/core-image-minimal-qemuriscv64.ext4,if=none,format=raw \
   -device virtio-blk-device,drive=disk0 \
   -object rng-random,filename=/dev/urandom,id=rng0 \
   -device virtio-rng-device,rng=rng0 \
   -kernel ./tmp-glibc/deploy/images/qemuriscv64/Image \
   -append 'root=/dev/vda rw highres=off  console=ttyS0 mem=512M ip=dhcp earlycon=sbi ' \
   -show-cursor  -nographic -machine virt -m 512 -serial mon:stdio -serial null 

The above command will open up SSH and telnet ports which can be used to communicate with the guest. It will also pass in host entropy to the guest, allowing entropy to be available on boot.

NOTE: When using OpenEmbedded it is recommended to use the runqemu script to boot QEMU. It will dynamically handle display options as well as advanced networking

Booting 32-bit Buildroot Images

Clone the Buildroot source code and cd into the directory.

Generate the default config:

 make qemu_riscv32_virt_defconfig

Build the images

 make

Boot the images:

 qemu-system-riscv32 \
   -M virt -nographic \
   -kernel output/images/fw_jump.elf \
   -device loader,file=output/images/Image,addr=0x80400000 \
   -append "root=/dev/vda ro" \
   -drive file=output/images/rootfs.ext2,format=raw,id=hd0 \
   -device virtio-blk-device,drive=hd0 \
   -netdev user,id=net0 -device virtio-net-device,netdev=net0

Booting 64-bit Buildroot Images

Clone the Buildroot source code and cd into the directory.

Generate the default config:

 make qemu_riscv64_virt_defconfig

Build the images

 make

Boot the images:

 qemu-system-riscv64 \
   -M virt -nographic \
   -kernel output/images/fw_jump.elf \
   -device loader,file=output/images/Image,addr=0x80200000 \
   -append "root=/dev/vda ro" \
   -drive file=output/images/rootfs.ext2,format=raw,id=hd0 \
   -device virtio-blk-device,drive=hd0 \
   -netdev user,id=net0 -device virtio-net-device,netdev=net0

Attaching GDB

To attach GDB to a QEMU RISC-V instance with only a single cluster (every machine except the sifive_u) run these commands from GDB:

 target extended-remote :1234
 info threads

To attach GDB to a QEMU RISC-V instance with multiple clusters (the sifive_u) run these commands from GDB:

 target extended-remote :1234
 add-inferior
 inferior 2
 attach 2
 set schedule-multiple
 info threads

The above commands assume the default GDB port exposed from QEMU of 1234. This will happen when you run QEMU with the '-s' command line argument.

If you would like QEMU to not run the guest until you have connected GDB, you can specify the '-S' command line argument as well.

Links

• Fedora RISC-V wiki
• OpenEmbedded meta-riscv
• Video: QEMU Support for the RISC-V Instruction Set Architecture

Contacts

Maintainers:

• Palmer Dabbelt
• Alistair Francis
• Sagar Karandikar
• Bastian Koppelmann